Scratch

I tried something like that, but it didn't work.

Just use this:

when gf clicked
forever
 if <key [right arrow v] pressed?>
  change [xvel v] by (1)
 end
 if <key [left arrow v] pressed?>
  change [xvel v] by (-1)
 end
 set [xvel v] to ((xvel) * (.87))
 change x by (xvel)
 if <touching [level v]?>
  change y by (([abs v] of (xvel)) + (1))
  if <touching [level v]?>
   change y by ((0) - (([abs v] of (xvel)) + (1)))
   change x by ((0)-(xvel))
   set [xvel v] to ((xvel) / (2))
  end
 end  
 if <key [up arrow v] pressed?>
  change y by (-1)
  if <touching [level v]?>
   set [yvel v] to (10)
  end
  change y by (1)
 end
 if <(yvel) < [3]>
  change y by (-1)
  if <not<touching [level v]?>>
   change [yvel v] by (-1)
  end
  change y by (1)
 end
 set [yvel v] to ((yvel) * (0.9))
 change y by (yvel)
 if <touching [level v]?>
  change y by ((0) - (yvel))
  set [yvel v] to ((yvel) / (2.5))
 end
end